<!DOCTYPE html>
<html lang="en">
<head>
	<meta charset="UTF-8">
	<title>Document</title>
	<style type="text/css">
		#box{
			width: 50px;
			height: 50px;
			background: #f00;
		}
	</style>
</head>
<body>
	<input type="button" id="btn" name="" value="value">
	<div id="box"></div>
	<script type="text/javascript">
		var btn=document.getElementById('btn');
		var box=document.getElementById('box');
		  btn.onclick=function(){
			btn.style.background="#000";
			btn.style.color="#fff";
            box.style.width="500px";
            box.style.height="500px";
            box.style.background="blue";
		}
	</script>
</body>
</html>